<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        while(true) {
            var select = prompt('欢迎使用简易计算器:\n 1.加法运算;\n 2.减法运算;\n 3.乘法运算;\n 4.除法运算;\n 5.退出;\n 请输入您的选项');
            if (select == '1') {
                var num1 =prompt('请输入第一数值:');
                var num2 = prompt('请输入第二个数值');
                alert(parseFloat(num1) + parseFloat(num2));
            } else if (select == '2'){
                var num1 =prompt('请输入第一数值:');
                var num2 = prompt('请输入第二个数值');
                alert(parseFloat(num1) - parseFloat(num2));
            } else if (select == '3'){
                var num1 =prompt('请输入第一数值:');
                var num2 = prompt('请输入第二个数值');
                alert(parseFloat(num1) * parseFloat(num2));
            } else if (select == '4'){
                var num1 =prompt('请输入第一数值:');
                var num2 = prompt('请输入第二个数值');
                alert(parseFloat(num1) / parseFloat(num2));
            }else if (select == '5'){
                alert('正在退出');
                break;
            }
            
        }
    </script>
</head>
<body>
    
</body>
</html>